[OpenLayers-Dev] On the relationship between ka-Map and OpenLayers

Christopher Schmidt crschmidt at metacarta.com
Wed Apr 8 20:39:30 EDT 2009


For several years, thre has been an outstanding ticket in OpenLayers,
http://trac.openlayers.org/ticket/327 , which I have meant to spend some 
on to help explain why I don't feel that the fixes in question are
appropriate for OpenLayers, and what I hope that users who are
interested in the ticket will do.

ka-Map provides two core pieces of functionality: a web-mapping API
similar to OpenLayers, and a PHP-based tile caching engine similar to
TileCache. In OpenLayers, we have ka-Map layers that support the use of
existing ka-Map tile setups using the PHP scripts of the ka-Map project.

Included in the OpenLayers 'examples' directory is a simple ka-Map
"like" example kamap.txt file. This file was a combination of a couple
different ka-Map files -- config.php and tile.php -- designed to be
primarily for people 'getting started' with ka-Map, not for long term

Any changes in the PHP code, I believe, belong within the ka-Map
project. The kamap.txt example file should probably be *removed* from
OpenLayers; it's misleading to include it there.

If there are changes neccesary in the *client* side code, I'm perfectly
willing to support them. The ka-Map changes suggested thus far have all
been entirely in the ka-Map PHP code, so far as I've seen -- with the
exception of a small change at the bottom of
which can be easily overriden by correctly configured clients, I

http://trac.openlayers.org/attachment/ticket/327/KaMap.patch is actually
the same patch, I believe.

Now, this particular change isnt' clear to me why it's needed, because
you can override 'i' in your client side code. However, the rest of the
changes -- splitting kamap.txt back up, etc. -- I believe these belong
in the ka-Map Project.

I'd love to see more effort put towards maintaining the ka-Map server
side code -- and maybe, if the project is interested, even supporting it
as a sort of 'mapserver tilecache for php' library. I'd be happy to have
the project share some mental space with tilecache towards that end, if
it's helpful.

Looking at the ticket description, "Except - if the image type is PNG in
config.php, and GIF in the layer constructor, and the layer is not a
base layer, the GIF is created with a white background color, instead of
a transparent background color." is the client side problem.

This seems like a clientside misconfiguration to me, and I don't see how
making things not use default parameters helps. 

With that in mind, it is my opinion that:
 * #327 is probably a combination of server-side bugginess and
   client-side misconfiguration. 
 * The former should not be fixed in OpenLayers, and kamap.txt should be
   removed from OpenLayers.
 * The latter should be fixed by not misconfiguring the client.

For now, I'm going to bump this to 2.9; if we haven't heard anything new
in the near future, I'm likely to simply close it. 

Comments welcome.

Christopher Schmidt

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